Yup, with AV off (or passive) then XP is relatively snappy on by today's standards relatively low end hardware. Win2K even more so. (having said that the UI of Win95 on a P90 flies in comparison to a modern computer with the vast bulk of IE glued into its UI)
Got caught by a real one once in 1988 by booting of a friends Amiga floppy - nothing since.
Other than sweeping virus laden emails into the bin, they are far less of a threat these days.
Professionally written malware and trojan downloaders that attempt to climb on from compromised web sites however are far more of a threat - it seems to be where most of the dead machines presented to us were brought down.
Indeed. Not too hard on a desktop system in some cases. A bit more tricky on a laptop of you are taking it to client sites and joining it to possibly compromised networks.